docs: def builder_from_source(source, filename, system_includes,
                          nonsystem_includes, quiet=False):
      """Utility method that returns an ASTBuilder from source code.
  
      Args:
        source: 'C++ source code'
        filename: 'file1'
  
      Returns:
        ASTBuilder
      """
      return ASTBuilder(tokenize.get_tokens(source),
                        filename,
                        system_includes,
                        nonsystem_includes,
                        quiet=quiet)